: Aim 1 is to generate and characterize 10 IgG monoclonal aCLs. Aim 2 is to analyze monoclonal aCLs in the in vivo fetal loss model. Aim 3 is to identify and characterize the mimetics for pathogenic aCL. Aim 4 is to do immunological and functional studies of antibodies against mimetics in APS patients. Aim 5 is to apply mimetics to study pathogenic aCL in APS patients and controls.